Rotatable tool for chip removing machining as well as a loose top and a basic body therefor

Abstract

A rotatable tool for chip removing machining, including a basic body having front and rear ends between which there extends a first geometrical center axis, and a loose top having front and rear ends between which a second geometrical center axis extends. The front end of the basic body includes a jaw, which is delimited by two drivers and an intermediate bottom and in which a part of the loose top is received. A centering pin protrudes axially rearward from the loose top and is inserted in an axial center hole, which mouths in the bottom of the jaw and in which a threaded hole mouths for a screw co-operating with the center pin. The center hole includes a cylindrical support surface, which is concentric with the center axis of the basic body and against which the centering pin of the loose top is pressed by the screw.

What is claimed is: 
     
       1. A rotatable tool for chip removing machining, comprising:
 a basic body having front and rear ends between which there extends a first geometrical center axis (C 1 ) around which the basic body is rotatable in a predetermined direction of rotation; and 
 a loose top having front and rear ends between which a second geometrical center axis (C 2 ) extends; 
 the front end of the basic body including a jaw, which is delimited by two drivers and an intermediate bottom and in which a part of the loose top is received, 
 a centering pin protruding axially rearward from the loose top being inserted in an axial center hole, which mouths in the bottom of the jaw and in which a threaded hole mouths for a screw co-operating with the center pin, 
 the center hole including a cylindrical support surface, which is concentric with the center axis (C 1 ) of the basic body and against which the centering pin of the loose top is pressed by the screw, 
 the centering pin of the loose top including first and second diametrically opposed, external surfaces, each having an axial extension and a peripheral extension, the first external surface forming a contact surface that is pressed against the support surface of the center hole and extends tangentially between two axially extending boundary generatrices, which are situated along an imaginary first circle (S 2 ) having a first center (MP 2 ) coinciding with the center axis (C 2 ) of the loose top, and between which an arc angle (β) is less than 180°, the second external surface forming a clearance surface that lacks contact with the inside of the center hole as a consequence of the cross-sectional area of the centering pin being smaller than the cross-sectional area of the center hole, 
 wherein the imaginary first circle (S 2 ) has a first radius (r 2 ) that is equally great as a second radius (r 1 ) of an imaginary second circle (S 1 ) having a second center (MP 1 ) coinciding with the center axis (C 1 ) of the basic body and that includes the cylindrical support surface of the center hole, and 
 wherein a greatest radial distance (RD 2 ) between the center axis (C 2 ) of the loose top and a point on the clearance surface of the centering pin is greater than the first radius (r 2 ) of the imaginary first circle (S 2 ) but smaller than a corresponding distance (RD 1 ) between the center axis (C 1 ) of the basic body and a clearance surface situated in the center hole and opposite the support surface. 
 
     
     
       2. The tool according to  claim 1 , wherein the contact surface and the clearance surface of the centering pin extend from a free end of the centering pin to prevent an incorrect insertion of the centering pin even partially into the center hole. 
     
     
       3. The tool according to  claim 1 , wherein a seat is countersunk in the clearance surface of the centering pin for cooperation with the screw, the seat being spaced apart from a free end of the centering pin and including a bottom surface and a stop surface situated axially rearward of the bottom surface. 
     
     
       4. The tool according to  claim 3 , wherein the bottom surface and stop surface of the seat are plane and form an obtuse angle with each other. 
     
     
       5. The tool according to  claim 1 , wherein the center hole in the basic body has a cross-sectional shape in which the clearance surface of the center hole includes two part surfaces interconnected by a concave part surface and wherein the two part surfaces converge toward the concave part surface. 
     
     
       6. The tool according to  claim 1 , wherein the center hole in the basic body has an oval cross-sectional shape in which the clearance surface of the center hole includes two part surfaces that extend parallel to each other in a direction from the support surface toward the concave part surface. 
     
     
       7. The tool according to  claim 5 , wherein the centering pin of the loose top has a cross-sectional shape in which the clearance surface of the centering pin includes two part surfaces that converge in a direction from the contact surface toward a back surface of the clearance surface. 
     
     
       8. A loose top for rotatable tools for chip removing machining, comprising:
 a head including front and rear ends between which a geometrical center axis (C 2 ) extends; and 
 a centering pin protruding axially rearward from the rear end of the head, the centering pin including first and second diametrically opposed, external surfaces, each having an axial extension and a peripheral extension, the first external surface forming a contact surface that extends peripherally between two axially extending boundary generatrices, which are situated along an imaginary circle (S 2 ) having a center (MP 2 ) coinciding with the center axis (C 2 ), and between which an arc angle (β) is less than 180°, the second external surface forming a clearance surface that extends peripherally from the two axially extending boundary generatrices and includes two part surfaces and a back surface, 
 wherein the rear end of the head has a radially extending plane surface that extends radially outward of the contact surface and the clearance surface relative to the geometrical center axis, 
 wherein, in a plane perpendicular to the center axis (C 2 ) at a first axial position of the centering pin, a first radial cross-section of the centering pin includes a first contact surface and a first clearance surface, 
 wherein, in the first radial cross-section, a greatest radial distance (RD 2 ) between the center axis (C 2 ) and a point on the first clearance surface is greater than the radius (r 2 ) of the imaginary circle (S 2 ) containing the first contact surface, and 
 wherein, in the first radial cross-section, the two part surfaces converge in a direction from the first contact surface toward the back surface of the first clearance surface. 
 
     
     
       9. The loose top according to  claim 8 , wherein the contact surface and the clearance surface of the centering pin extend axially forward from a free end of the centering pin. 
     
     
       10. The loose top according to  claim 8 , wherein a seat is countersunk in the clearance surface of the centering pin for cooperation with a screw, the seat being spaced apart from a free end of the centering pin and spaced apart from the first axial position, and wherein the seat includes a bottom surface and a stop surface situated axially rearward of the bottom surface. 
     
     
       11. The loose top according to  claim 10 , wherein the bottom surface and the stop surface are plane and form an obtuse angle with each other. 
     
     
       12. A basic body for rotatable tools for chip removing machining, comprising:
 an envelope surface and front and rear ends, between which a geometrical center axis (C 1 ) extends, 
 wherein the front end includes jaw delimited by two drivers and an intermediate bottom in which an axially extending center hole mouths, a hole for a screw extending between the center hole and the envelope surface, 
 wherein the center hole is delimited by a cylindrical support surface, which is concentric with the center axis (C 1 ) and which is positioned on a portion of a circle (S 1 ) having a radius (r 1 ), and by an opposite clearance surface situated radially outside an imaginary projection of the circle (S 1 ), and 
 wherein the center hole has a cross-sectional shape in which the clearance surface includes two part surfaces. 
 
     
     
       13. The basic body according to  claim 12 , wherein the two part surfaces converge toward a concave part surface included in the clearance surface. 
     
     
       14. The basic body according to  claim 12 , wherein the two part surfaces extend parallel to each other from the cylindrical support surface toward a part surface that has a semi-cylindrical shape. 
     
     
       15. The basic body according to  claim 14 , wherein the cross-sectional shape of the center hole has an oval shape. 
     
     
       16. The tool according to  claim 5 , wherein the centering pin of the loose top has a cross-sectional shape bounded by a contact surface,
 wherein a first portion of the contact surface is cylindrical and extends between two boundary generatrices along the arc, and 
 wherein a second portion of the contact surface includes a pair of convex transition surfaces and a pair of plane part surfaces that converge in a direction from the first portion of the contact surface toward a convex back surface of the clearance surface. 
 
     
     
       17. The loose top according to  claim 8 , wherein the two part surfaces are planar,
 wherein the clearance surface includes a pair of convex transition surfaces, and 
 wherein, in the first radial cross-section, the two part surfaces are connected to the contact surface by the transition surfaces. 
 
     
     
       18. The tool according to  claim 1 , wherein the center hole in the basic body has a cross-sectional shape in which the clearance surface of the center hole includes two part surfaces separated by a concave part surface, and wherein the two part surfaces (a) join to the support surface non-tangentially or (b) extend parallel to each other toward the concave part surface. 
     
     
       19. The tool according to  claim 18 , wherein, when the two part surfaces join to the support surface non-tangentially, the two part surfaces are interconnected by a concave part surface and the two part surfaces converge toward the concave part surface. 
     
     
       20. The tool according to  claim 18 , wherein, when the two part surfaces extend parallel to each other toward the concave part surface, the two part surfaces to provide the center hole in the basic body an oval cross-sectional shape in which the clearance surface of the center hole includes two part surfaces that extend parallel to each other in a direction from the support surface toward the concave part surface.